Peer-to-peer electronic file sharing over a public network is known. Some peer-to-peer networks use prolific copying of files to enable distributed file sharing. For some types of data and/or some types of digital industries, such a distributed approach may not be sufficiently secure. Bi-directional file synchronization over a public network is known. Some file-synchronization services use cloud storage for electronic files. For some types of data and/or some types of digital industries, a file-synchronization approach may not be sufficiently secure. Secure file sharing, for example through encryption, authorization, password protection, etc., may be known.